1. Field of the Invention
The present invention relates generally to a headlight mounted on a vehicle. More particularly, the present invention relates to a headlight exclusively usable for irradiating a light beam for a vehicle passing by in the opposite direction (hereinafter referred to simply as a headlight).
2. Background Art
To facilitate understanding of the present invention, a typical conventional headlight of the foregoing type will briefly be described below with reference to FIG. 5. The headlight designated by reference numeral 90 includes a light source 91 composed of a filament in a halogen lamp and a reflective mirror 92 arranged behind the light source 91, and wherein a focus f of the reflective mirror 92 having a contour of revolving parabolic plane is located at the shown position on an axis line of the light source 91. As shown in FIG. 5, a lower half of the light source 91 is covered with a hood 93. With this construction, since the focus f of the reflective mirror 92 is located behind the light source 91, only the reflected light beam reflected from an upper half of the reflective mirror 92 is practically used for the purpose of irradiating a light beam for a vehicle passing by in the opposite direction. Consequently, the headlight 90 exhibits light distribution properties for irradiating a light beam for a vehicle passing by in the opposite direction without irradiation of any dazzling light beam, i.e., an upward oriented light beam.
It should be added that a lens (not shown) is disposed at the position located forward of the reflective mirror as seen in the light irradiating direction so that the light distribution properties of the headlight 90 having a fundamental configuration is optimized in cooperation with the light source 91 with the reflective mirror 92.
With the conventional headlight. 90 constructed in the above-described manner, however, since the desired light distribution properties of the headlight 90 are obtainable by covering the lower half of the light source 91 with the hood 93, merely about a half of the light beam irradiated from the light source 91 can actually be utilized for the afore-mentioned purpose. Consequently, the headlight 90 is visually recognized with less brightness compared with the electricity practically consumed by the light source 91. In other words, the headlight 90 has a problem that it practically utilizes only a part of the light beam generated by the light source 91, resulting in the headlight 90 operating at a low efficiency.